What is android_secure 12/31/1969

This appeared in file manager with tons of my pics and videos gone. I seen where few other ppl had same priblem. I would like to know what caused this. I don't know if the same ppl also had trouble with their camera afterwards like it was hacked into and the hacker was adding to their pics, sounds crazy well it is and I would like to know if any other 12/31/69 victims had same problem. Also best way to retrieve if possible lost/ stolen files